Michener writes in a semi-documentary style. The topics explored in the novel include naval warfare in the Pacific, air combat in the Korean War (something Michener had already explored in The Bridges at Toko-Ri), test pilot life at 'Pax River', astronaut selection and training, the role of the media in promoting the space program as a national achievement, and the development of the Gemini and Apollo spacecraft, the rise of the military-industrial complex and the evolution of NACA into NASA.

The story begins in 1944 and covers more than 30 years in the lives of four men and their families: Dieter Kolff, a German rocket scientist who worked for the Nazis; Norman Grant, a World War II hero turned U.S. Senator from a fictional state; Stanley Mott, an aeronautical engineer invested with a top-secret U.S. government mission to rescue Kolff from Peenemünde; and John Pope, a small-town boy turned Naval Aviator who becomes a test pilot and then astronaut. Randy Claggett, a rambunctious Marine Corps aviator and astronaut is considered by Michener to be the most important supporting character (the first two parts of the book are entitled "Four Men" and "Four Women"). The lives of the fictional characters interweave with those of historical figures, such as Wernher von Braun and Lyndon Johnson. A whole group of trainee astronauts are introduced to fly fictional but plausible Project Gemini and Project Apollo missions; the intensive training and jockeying for position amongst the astronauts forms much of the background of the middle of the novel, reminiscent of a fictional version of Tom Wolfe's The Right Stuff and the movie as well.

Michener dramatizes the life experiences of these men and their families against the backdrop of the real history of the U.S. space program, depicting their experiences in post-war aviation, the space race between the United States and the Soviet Union; the development of congressional funding for the space program; the early failures in the Gemini program; and the successful moon landings in the Apollo program. In a fictional postscript to history, Michener creates a last, "Apollo 18" launch to further the drama of Pope, Claggett and Linley, America's first black astronaut. This is the only Apollo mission in which the lunar module lands on the far side of the Moon, unseen by Earth; in order to remain in contact with NASA after landing, while still in lunar orbit the Apollo craft must launch a communication satellite that will bounce the lunar module's signals to Earth. An unusually high amount of sunspot activity, only partially predicted by the NASA ground crew, results in the death of Claggett and Linley in the lunar module when they are exposed to lethal levels of radiation following their ascent back towards the command module and they crash back into the lunar surface; Pope, the command module pilot returns to Earth safely. The mission profile is significantly different from that of the real-world canceled mission that would have been Apollo 18.

On the human side, various subplots run through the novel, contrasting the "official" heroism of NASA with the human fallibilities of the cast—the difficulties the Kolffs face in integrating into American society; Norman Grant's initial embrace of the space program and his abandonment of it as it no longer serves his political aims, while his unstable wife and their daughter fall in with a highly intelligent but cynical cult leader calling himself Leopold Strabismus who exploits first the UFO craze and then an anti-scientific creationist agenda to increase his fortune; Randy Claggett's womanizing; the contrast between Stanley and Rachel Mott's ordered, rational existence and their troubled relationship with their sons, and John Pope's unusual yet supportive relationship with his lawyer wife Penny.

The novel closes with Pope retired from NASA and a respected professor of astronomy, his wife Penny in the Senate, and Mott consulting on "Grand Tour" unmanned missions to the outer solar system. The two men finally attending a NASA workshop discussing the possibility of extraterrestrial life, at which Strabismus privately drops the creationist/fundamentalist persona he has adopted and joins in the intellectual debate on the inevitability of life elsewhere in the Universe.

Allusions/references to actual history, geography and current science[edit]